The world is waking up to the calamity that is HIV/Aids, the United Nations secretary general, Kofi Annan, said yesterday, setting a new tone of hope at a three-day summit in New York devoted to the epidemic.

"This year we have seen a turning point," he said. "Aids can no longer do its deadly work in the dark. The world has started to wake up. We have seen it happen in the media and public opinion - led by doctors and social workers, by activists and economists and, above all, by people living with the disease.

"We have seen it happen among governments and ... in the private sector. Never ... has there been such a moment of common purpose."

Leadership was fundamental if the world was to conquer the disease, Mr Annan said. "All of us must recognise Aids as our problem. All of us must make it our priority."

The US secretary of state, Colin Powell, reaffirmed Washington's commitment with a call to action, saying: "Our global response to this scourge has been woefully inadequate."

Mr Powell drew comparison with the bubonic plague, but pointed out that science had given the 21st century the means to understand and tackle Aids.

But now was the time to act, he said. "Will history record a moment in our time, on our watch when help came too late?"

He said he knew "of no enemy in war more invidious or dangerous than Aids".

Mr Powell defended the US donation of $200m (£140m) to the global health fund set up by Mr Annan, which has been criticised as inadequate considering the huge sums - $7bn to $10bn a year - needed to prevent and treat Aids, and look after, such as the 15m orphans, affected by the disease.

He described the donation as "seed money" which might "generate billions more".

Washington would put in more money "as we learn where our support can be most effective". The US has made it clear that it is most in terested in helping countries such as Uganda which have learned to help themselves.

He also promised to give training for specialists, nurses and technicians, and that Cuba would make anti-retroviral drugs - the costly medicines that keep people in the west with HIV infections healthy - for 30,000 patients if the world community contributed the raw materials.